JP4448573B2 - Molds and molding elements for making cuts in rubber products by molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tire mold having at least one molding element designed to make a cut in a tire by molding, and the invention also relates to a molding element designed to make a tire cut by molding.
[0002]
BACKGROUND OF THE INVENTION
In order to make a cut in the tire tread by molding, a mold composed of a plurality of molding members is usually used, and each molding member has a plurality of molding elements protruding on these molding surfaces. The term “cut” includes grooves (width of at least 3 mm) and notches (grooves of width of 3 mm or less).
[0003]
The molding element generally consists of two parts, the first part forming the molding part of the molding element projects on the molding surface of the mold and the second part as an extension of the first part is in the mold. It is fixed. The fixing of the second part is obtained, for example in the case of a mold made by casting, during the casting of the material constituting the mold, which captures the second part of the molding element during its cooling phase.
[0004]
During the molding and vulcanization of the tire, the molded part of the molding element is submerged in the rubbery component of the tire in order to make a cut. After vulcanization of the tire, mold components are released by moving the mold components in the direction of removal from their correct mold and gradually separating them from each other, carrying the molding elements together with these components and taking them out of the tire. To do.
[0005]
In order to produce tires with good rolling performance, incisions are often used, and the geometry and / or average orientation of such incisions is significant along with efforts to wear tire treads. Technical improvements have been made. However, in general, when such a cut is formed using a rigid molding element, it may be very difficult to extract the molding element from the mold (hereinafter, the extraction from the mold may be simply referred to as “extraction”). Yes (since extraction requires a force that increases as the number of molding elements used increases), it is impossible to extract without fear of damaging the tire (it may tear off rubber compound parts) ).
[0006]
For example, French Patent No. 2,722,145 discloses a tread having a plurality of embossed elements, some of which comprise incisions, the average of such incisions on the rolling surface. The target direction gradually changes as the tread wears. As soon as the change in orientation is greatest, obtaining such a cut with a molding element consisting of a rigid wire forming a molded part of the same geometric shape is at least in the extraction stage (in other words, the extraction stage of the molding element). Have difficulty. The term “wire” is intended to include blades.
[0007]
The same is true if the molding element has at least one rigid shape that has a helical or twisted shape or any geometric shape that requires the presence of torque resulting from the twist exerted on the molded part during extraction. This is the case with wires. The use of this type of element in order to ensure that the appearance of the tread is not impaired during the extraction operation requires specific precautions which are usually incompatible with industrial production requirements.
[0008]
SUMMARY OF THE INVENTION
In order to solve these drawbacks, a mold for molding a tire tread has been proposed. This mold is composed of a plurality of members, and each of the mold members (hereinafter also referred to as “molded members”) is the surface of the tread. It has a molding surface for molding a part of the mold, and can move in the molding direction and the direction of extraction from the mold.
[0009]
In addition, the at least one forming member comprises at least one forming element making at least one incision in the tread, the forming element having two parts, one provided as an extension of the other The first part is a molded part of the molding element and protrudes on the molding surface in order to make a cut in the tire, and the second part has an axis XX ′ that coincides with the molding direction and the direction of extraction from the mold. It can rotate around and fits within a seating section provided on the molded member.
[0010]
The forming member comprises means for attaching and fastening the second part of the forming element in a seat provided in the mold, the attaching means having the axis XX 'on its forming element at least during the extraction stage from the mold. It can be rotated as a center.
[0011]
The first part of the molding element is adapted to make at least one incision in the tire, for which purpose the first part has at least one wire, the geometric shape of which is During the extraction, the contact force of the rubber around the first part produces a torque around the main direction XX ′ of the molding element that tends to rotate the molding element about the resulting XX ′. The free-rotating attachment of the molding element makes it easy and easy to remove the molded part of the molding element from the tire during extraction.
[0012]
In an alternative embodiment, the second part of the molding element is attached to a cylindrical base in a freely rotating state, and the base is configured to be rotatably and rigidly attached within a seating portion provided on the molding member. By comprising in this way, abrasion of the shaping | molding member by friction with the rotationally-moving component of a shaping | molding element can be prevented.
[0013]
In order to facilitate the insertion and / or removal of the molded part from the rubber, it is advantageous to combine the relative rotational movement of the molding element with respect to the mold and the translational movement of the same molding element with respect to the mold. For this purpose, a generally cylindrical seating part having a main axis XX ′ is provided for receiving the molding element, and the part of this molding element inserted into the seating part is in the direction XX ′ above. In addition, means are provided for moving the molding element in the direction of XX 'within the seat. It is also preferable to provide complementary means for ensuring a given position of the molding element in the molding structure.
[0014]
Regardless of whether there is a risk of displacement of the molding element in the seating section, it is important to provide a rotation means before or during the molding and / or sampling operation. It is advantageous if it can be synchronized with the movement of the forming element along (which corresponds to the pulling movement of the hub and / or the movement of the forming element in the seat).
[0015]
As is well known, the molding elements used to make the cuts in the tire are formed directly on the mold used to mold the tire during the manufacture of the mold, or they can be formed separately, Is slid onto the mold during or after manufacture. Mold manufacturing methods and tire forming methods limit the possibility of matching the shape of the cut to a shape that allows the rubber compound to be extracted from the mold without being cut or torn after vulcanization.
[0016]
Molding elements that make it possible to make non-peelable cuts (ie with undercut parts) are known, for example, from French patent application No. 97/0594. To use, it is necessary to deform the molded part during extraction, and this deformation may become more or less permanent after most molding.
[0017]
In order to solve these problems, a molding element is proposed that is attached to a molding member that molds a rubber compound product, such as a tire or a tractor tread, in order to make at least one incision in the tire. It is possible to drive the molding movement and / or the extraction movement from the mold in the direction. The molding element of the present invention has a body with a head that is an extension of the molded part, the molded part protruding from the molding surface of the molded member to make at least one cut in the rubber compound tread. And the head has at least one cylindrical body with an axis XX 'defining the main axis of the molding element and means for mounting the molding element in the molding member, the means being such that the molding part of the molding element is in the direction XX'. When subjected to an acting force or torque about the same direction XX ', it cooperates with the forming member to allow rotation of the head about XX' relative to the mold while retaining the forming element in the direction XX '. It is characterized by that.
[0018]
The molded part of the molding element according to the invention has at least one wire fastened at one of its ends to the head of the molding element and extending at least locally in a direction that is not at an angle of 0 ° with the direction XX ′ The molded part receives a force exerted by the rubber compound during extraction, and the resultant force becomes a torque acting around the direction XX ′.
[0019]
This molding element allows the formation of cuts that cannot be removed immediately, and the geometric shape of the molded part of the molding element has at least partly a spiral or twisted shape. “Partial” means that the incision has a helical profile only in part of its length.
[0020]
In one embodiment of the molding element that makes it possible to obtain a mold according to the invention, the molding element comprises attachment means for attaching and fastening it to the molding member, the attachment means being concentric with the head of the molding element. The base is configured to be rotatably fitted in a seat provided on a molding member that supports the molding element. This base is designed to cooperate with the head of the molding element in order to be able to rotate the head relative to the base and consequently with respect to the molding member carrying the molding element.
[0021]
The molded element of the present invention solves the problems that arise in the case of spiral geometries that are difficult if not impossible to remove from the mold, and a molded part that supports the molded element of the present invention. When displaced, the mechanical action of the rubber compound around the molding element on the resulting molding element causes the molding element to move in its main direction (direction approximately perpendicular to the molding surface of the mold or slightly from the molding surface, ie at most 15 °). Rotate around an angle (inclined direction).
[0022]
The mold and molding element of the present invention will be better understood from the description of several embodiments, which will be described with reference to the drawings and not limit the present invention.
[0023]
[Description of Preferred Embodiment]
FIG. 1 shows a partial cross-section of a molded part 1 of a tire tread, which has a molded element 2 that is cut into an average shape of a helix of axis XX ′ by molding. It is attached. The illustrated molding member 1 has a molding surface 3 adapted to mold a part of the rolling surface of the tire tread, and has a cylindrical shape with an axis XX ′ extending in the molding member 1 and on the rolling surface 3. A groove 4 is provided (by molding or machining), and its trace on the molding surface is circular and of inner diameter D. In this figure, the groove 4 has a generally rectangular cross section.
[0024]
The molding element 2 is constituted by a cylindrical head 7 which is adapted to be fitted into the groove 4, and is provided with a molding part 5 as an extension of the head 7, the molding part 5 having a single rectangular cross section. It consists of wire 6 and forms a helical part around XX '. The molding element is made of a material, such as a metal, that is sufficiently rigid to penetrate the raw rubber during molding.
[0025]
In addition, a fastening means 10 projecting on the outer wall surface of the head 7 of the forming element 2 is provided with a groove 9 provided on the wall 8 of the groove 4 serving as a seating part of the forming element located farthest from the axis XX ′. It is provided to work together. The fastening means 10 shown schematically exerts an elastic force directed radially outward with respect to the axis XX ′ and allows the molding element 2 to be mounted while allowing the molding element to rotate freely within its seat. To.
[0026]
At the time of extraction after vulcanization, the rubber around the wire 6 reacts against the wire 6, thereby generating a torque centered on XX ′. By rotating in the seat 4 as a center and following the notch geometry provided by molding in this way, the wire can be unwound from rubber without damaging the molded tread.
[0027]
In the case of a mold according to another embodiment of the invention whose partial cross section is shown in FIG. 2, the seat 21 provided on the mold 1 'to receive the form element 20 is perpendicular to the molding surface 3' of the molding member. It has the shape of a cylindrical hole with a simple axis XX '. As a matter of course, it may be possible to form an overall cylindrical seat having an axis that is at an angle different from 90 ° with the molding surface of the molded member so that a cut can be made, and its average axis. Is inclined from a direction perpendicular to the molding surface, in which case it is desirable to provide an angle equal to or slightly different from the angle caused by the direction of withdrawal of the molded part.
[0028]
The main body of the molding element 20 includes a molding part 22 formed by a blade 23 having a rectangular cross section spirally wound around XX ′. The molding part 22 is an extension of a cylindrical head 24 and has a circular shape. The dimensions of the columnar head are suitable for being arranged with an appropriate gap inside the seating portion 21, which allows the head to be placed in the seating portion and the head to rotate within the seating portion and the head. And so as to reduce rubber penetration between the seat and the seat.
[0029]
Similar to what has been described for the embodiment shown in FIG. 1, fastening means 26 (e.g., snap rings or retainers) are provided on the head 24 of the molding element, thereby inserting the head into its seat 21. In addition, once in place, the fastening means cooperates with a circular groove 27 provided in the wall 25 of the seat.
[0030]
What has just been described for wires is the case of a molded element having a molded part consisting of a plurality of wires parallel to each other, each forming a helix and allowing the molded element to rotate during extraction from the mold. Can be said as a whole.
[0031]
It is advantageous to carve the spiral drawn by each wire on a truncated cone so that the tire tread engraving pattern gradually develops as the tire tread wears, and each wire touches its small diameter base and coiled The virtual truncated cone to be rolled is located as close as possible to the head of the molding element (ie as close as possible to the molding surface of the mold supporting the molding element), and the angle of the truncated cone is preferably from 0 ° to 20 °. In the case of this type of molded element, the multiple molded elements are constructed so that the distance between them and the center of the narrow base circle is smaller than the center distance of the wide base, and somehow the molded part Can be knitted together.
[0032]
One particular embodiment of the molding element 30 of the present invention is shown in FIG. 3, which shows a cross section along a plane containing the axial direction XX ′ of this molding element.
[0033]
The body of the molding element 30 in FIG. 3 is composed of a molded part 31 formed by a wire 32 located in the extension of the cylindrical part of the axis XX ′ constituting the head 33 of this molding element.
[0034]
In addition, the molding element 30 has a third cylindrical part with an axis XX ′ identical to the axis of the head of the molding element, which third part forms the base 34 of the molding element. Inside, a molding element head 33 is housed rotatably around XX ′.
[0035]
By combining the provision of the rib 37 around the head 33 of the molding element and the provision of the groove 38 on the wall opposite to the base 34, the head can be rotated relative to the base while maintaining the assembled state. In order to facilitate mounting of the head 33 within the base 34, it may be provided with at least two cuts 36 in the head 33 and in the same direction as XX '.
[0036]
Of course, other attachment means and other fastening means can be used, and in particular means should be provided which allow the replacement of the base or the replacement of the molding element.
[0037]
In conclusion, the mounting of such a molding element of the body mounted in the base is performed by placing the base in a seat provided on the inside of the molding member. The advantage of such an arrangement is that the play between the rotating movable parts can be fine-tuned (in this case, the play between the base and the head) to reduce mold wear due to contact with the rotating movable parts.
[0038]
A shoulder 39 provided on the base opposite to the molded part is adapted to cooperate with means for connection (not shown) in the main direction XX 'of the molded element. The purpose is to prevent the molding element from being pulled out of its seat in the mold.
[0039]
In this variant of the forming element, for example, the base and the head are made possible by allowing the presence of a support provided on a conical support 35 of the axis XX ′ provided between the base 34 and the forming element 30. It is advantageous to use means for reducing the coefficient of friction between
[0040]
FIG. 4 shows a cross section along a plane including the axial direction of another embodiment of the forming element 40 of the present invention.
[0041]
The illustrated molding element 40 has a molded part formed by a wire 41 spirally wound about a direction XX ′ and a head 42 in the form of a hollow cylinder, where the head is inserted into a cylindrical base 46. 3 has the same configuration as that of the molding element of FIG.
[0042]
To make the extraction even easier, especially when using wires with complex geometries, the forming element is driven in both rotational and translational movement (eg by synchronizing these two movements). This arrangement is advantageous. For this purpose, a wall 44 located radially outside the cylinder forming the head 42 is provided with a groove 44 having a spiral track or track in the opposite direction as seen from the spiral formed by the wire 41 of the molded part, It has also been proposed to provide at least one rod 45 across the base 46 which cooperates with a groove 44 formed in the head. In this way, it is possible to control and adjust the rotation of the molded part under the action of the force exerted by the rubber at the time of extraction, and the rod 45 correctly sets the position of the molding element before molding. In order to do so, the rotational molding element can be locked.
[0043]
After extraction, the molding element shown in FIG. 4 takes the geometric shape shown in FIG. 5 and accordingly the head 42 of the molding element is partially located outside its base 46. In addition, an elastic return means may be provided for returning the molding element 40 to its molding position, the purpose of which is to reproduce the same cutting configuration for all tires provided with the molding element by molding.
[0044]
Another embodiment of the molding element of the present invention is shown in FIG. FIG. 6 shows a cross section of an alternative forming element 50 adapted to make two concentric cuts along a plane having the axis XX ′ of the forming element, each cut being in the form of a helix. Yes.
[0045]
The molding element 50 includes a cylindrical base 53, a first cylinder 51, and a second cylinder 52 as a whole of an axis XX 'that is fitted in a seat portion formed in the tire molding member 64. The cylinders 51 and 52 are respectively provided with wires 62 and 63 as extensions for forming a molded part of the molding element. The two cylinders 51, 52 are in contact with each other and have conical bearings 61, 61 'that allow the cylinders to rotate relative to each other about the axis XX'.
[0046]
The molding element is incorporated into a seat provided on the molding member in the manner shown in FIG. The conical bearings 60, 60 ′ are in contact with each other inside the base 53 and the radially innermost first cylinder 51 to allow the first cylinder to rotate relative to the base. It is provided on the radial wall.
[0047]
Furthermore, locking means 56, 58 for connecting the first cylinder and the base and locking means 57, 59, 55 for connecting the first cylinder and the second cylinder 52 are provided, Its purpose is to form a molding element to maintain the connection between the cylinder and the base and to allow free rotation of the cylinder about XX '.
[0048]
The wire 62 of the first cylinder 51 is advantageously geometric along a helix having an angle opposite to the sign of the angle of the helix formed by the wire 63 of the second cylinder 52 concentric therewith. The geometric contour is followed, so that the cylinders rotate in opposite directions at least during the extraction stage from the mold.
[0049]
In the latter case, the wire constituting the molded part of the first cylinder is in sliding contact with the wire of the molded part of the second cylinder, thereby creating a single cut and the opposite sides of this cut. It is also advantageous to form a kind of mesh that forms a plurality of openings that allow the rubber compound to pass through during molding to form a connecting bridge between the walls.
[0050]
The same configuration as above can be adopted when at least one cylindrical body is provided with several wires that all form a spiral that is parallel to each other, and the molded component of the molding element of the present invention has three or more cylindrical bodies. It is good to include.
[0051]
In all the embodiments described above, it is advantageous to have a configuration in which the cross-sectional area of each wire of the molded part decreases from its end fastened to the head of the molding element towards the opposite end of the molded part.
[0052]
It is also advantageous to have a construction in which each wire of the forming element is provided with a membrane that considerably reduces the force required for extraction.
[Brief description of the drawings]
FIG. 1 shows a molded part for molding a part of a tire tread comprising a cylindrical shaped element of an axis XX ′, which is attached to the molded part so as to be freely rotatable around an axis XX ′ within a seat in the form of a circular groove. FIG.
FIG. 2 is a sectional view of a mold with a seating portion in the form of a cylindrical hole in which a head of a molding element that can rotate about an axis XX ′ is housed.
FIG. 3 is a cross-sectional view of a molding element of the present invention having a cylindrical head provided in a freely rotating state inside a cylindrical base, showing the state where the base is configured to be fastened in the mold. It is.
FIG. 4 is a cross-sectional view of a modification of the molding element of the present invention, in which the cylindrical head provided in a freely rotating state inside the cylindrical base can move in the axial direction XX ′ of the base. FIG.
FIG. 5 is a cross-sectional view of a variation of the molding element shown in FIG. 4 in the extraction position.
FIG. 6 is a cross-sectional view of a modified embodiment of a molding element according to the invention formed by two concentric cylinders rotatably mounted on a cylindrical base adapted to be installed in place on a tire mold is there.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Molding member 2,20,30,40,50 Molding element 3 Molding surface 4 Cylindrical groove 5 Molded parts 6, 32, 41, 62, 63 Wire 7, 24, 33, 42, Cylindrical head 9 Groove 10 Fastening Means 51 First cylinder 52 Second cylinder

Claims (18)

A molding member (1, 1 ') for molding a part of a tire tread, wherein the molding member (1, 1') can move in a direction of extraction from a mold, and the molding member (1, 1 ') ) Has a forming surface (3) for forming the surface of the tread, the forming member (1, 1 ') being at least one forming element (2, 20 "for forming at least one incision in the tread. )
The molding element includes a first part (5, 22) and a second part (7, 24) that is an extension of the first part (5, 22), and the first part ( 5, 22) is a molded part of the molding element and protrudes from the molding surface (3) to make a cut in the tire, and the second part (7, 24) is from the molding surface (3), Having a cylindrical shape with a central axis XX ′ extending in the direction of extraction from the mold;
In a molding member adapted to be mounted in a recess (4, 21) provided in the molding member (1, 1 '), the molding member comprises:
Means for holding the second part of the molding element for free rotation in said recess, said holding means being able to rotate the molding element about its axis XX 'at least during the extraction stage from the mold I have to,
A molded member characterized by that. Said means for molding the molding element on the molding member consists of a cylindrical base (34, 46, 51) which can be fixed in place in a recess provided in the mold, the second part of the molding element being said Attached to the base in a freely rotating state,
The molded member according to claim 1. A recess provided to receive a molding element that can rotate about an axis XX ′ extends inside the mold and allows movement of the molding element in the direction of extension, and further allows the molding element to move in the recess XX ′. Means for moving in the direction of
The molded member according to claim 1. The means provided for moving the forming element in the recess in the direction of XX ' also allows a rotational movement of the action, which is in synchronism with the translational movement in the recess,
The molded member according to claim 3 . A molding element configured to be attached to a molding member to mold a tread,
In the molding element, wherein the molding member is adapted to make at least one cut in the tread, and the molding member can be driven in a mold drawing direction.
A body having a head with a molded part as an extension, the molded part protruding from the molding surface of the molded member to make at least one cut in the rubber compound tread;
Said head comprises a cylinder of an axis XX 'defining the main axis of the molding element and means for attaching the molding element to the molding member, said means acting on the force acting on the molding element in the direction XX' When subjected to torque about the same direction XX ', the molding element cooperates with the molding member to allow the head to rotate relative to the mold about XX' while holding the molding element in the direction XX '. Work,
The molded part of the molding element comprises at least one molding wire, one end of which is fastened to the head of the molding element and extending in a direction parallel to the XX ′ direction, and the body of the molding element is removed from the mold. When the rubber compound comes into contact with the blade, it is rotationally driven with respect to the base about the axis XX ′, and the holding of the base by the molding member facilitates the extraction from the mold.
A molding element characterized by that. At least one blade (32, 41, 62, 63) of the molded part forms a helix around the direction XX ′,
Molding element (30, 40, 50) according to claim 5. The molded part as a whole consists of a plurality of blades arranged parallel to each other, each of the blades forming a spiral,
The molding element according to claim 6. As the tire tread wears, the spiral constituted by the blades is inscribed in the truncated cone and the base of the narrowest diameter of the truncated cone is located as close as possible to the head of the forming element. The sculpture pattern of the tire tread is gradually generated.
Molding element according to claim 6 or 7. The angle of the truncated cone is in the range of 0 ° to 20 °,
The molding element according to claim 8. The head of the molding element is composed of at least two concentric cylinders having the same axis XX ′, each cylinder supports a molding blade, and further connects the cylinders to each other in the direction of XX ′. And means for rotating the cylinders relative to each other about the axis XX ′,
The molding element according to claim 5. One blade of the cylinder follows a geometric contour along a helix having an angle opposite to the angle of the helix formed by the blade of the other cylinder concentric with it, thereby at least the mold During the extraction stage from, the cylinders are designed to rotate in opposite directions,
The molding element according to claim 10. The body of the forming element consists of two concentric cylinders having an axis XX ', each cylinder supporting at least one spiral wound blade, each supported by the radially outermost cylinder The blade is in sliding contact with each blade supported by the inner cylinder, and has an angle with a sign opposite to the sign of the angle of the spiral formed by each blade supported by the innermost cylinder. Forming a spiral, thereby forming a mesh with openings through which the rubber compound passes to form a connecting bridge during molding,
12. A molding element according to claim 10 or 11. The cross-sectional area of the blade decreases from the end of the blade fastened to the head towards the opposite end of the molding element,
The molding element according to claim 5. The molding element of the mold has a base in the shape of a hollow cylinder of the axis XX ′, and the head of the molding element is provided inside the hollow cylinder, and the head is placed on the outer surface of the head. A groove cooperating with a raised element projecting on the inside of the cylinder forming the base, so that it can be rotated with respect to
The molding element according to claim 5. A groove provided on the outer surface of the head of the forming element has at least a part of the spiral geometry of the axis XX ′ and further protrudes on the inside of the base and cooperates with the groove A state element is provided, so that when the body of the molding element is subjected to a force along its axis XX ', the body can perform a translational movement simultaneously with a rotational movement with respect to the base. Yes,
The molding element according to claim 1. A bearing that reduces frictional force and facilitates rotational movement of the body of the body relative to its base;
16. A molding element according to any one of claims 5 to 15. The means for reducing the frictional force is a ball bearing;
The molding element according to claim 16.   A rubber compound tread molded with a mold having at least one molding element according to any one of claims 5 to 17.

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